Nigeria has started the massive task of registering voters in preparation for state and national elections but the complaints have also started.

Election officials say registration started smoothly at 120,000 centres for a massive 10-day operation to enfranchise the country's 60 million voters.

MPs have called for Obasanjo's impeachment

The major complaint about the first day of the registration exercise has come from one northern state and there have been reports that centres in some areas were late opening, according to the French news agency, AFP.

The BBC's Sola Odunfa in Lagos reported that registration was slow in Nigeria's commercial capital and many people chose to stay at work.

A senator from the northern state of Nassarawa told AFP that the electoral commission had refused to register voters in the Toto region of his state.

He said this amounted to unfair exclusion.

Danger of violence

Electoral commission told Nigerian state radio that its officials were not in the district because of fears that their presence could provoke unrest in an area that has been troubled by ethnic clashes.

Senator Mohammad Abubakar did not accept the this saying that "for five years there has been no crisis in Toto".

Obasanjo is facing possible impeachment

" I can't see why the people should not be allowed the right to vote", he told AFP.

He said it was a deliberate attempt to disenfranchise the Toto community for political reasons.

Presidential elections must come before the current term of President Olusegun Obasanjo - now threatened with impeachment - ends in May.

The electoral commission has called on all voters to register and to see it as the first part of the elections.

Observers say delays to the registration process have put real pressure on authorities to hold that poll, as well as state votes, within the timeframe specified by the constitution.

Votes postponed

Local elections have already twice been postponed because the electoral roll has not been updated, breaking a constitutional deadline.

The registration delays have been caused by a lack of funding from the central government, and public disagreements with the president, the BBC's Nigeria correspondent, Dan Isaacs, reports from Abuja.

Now, the registration is the first real test for the much-maligned electoral commission, our correspondent says.

In the Palm Grove and Ikorodu areas of Lagos, AFP reported that electoral commission staff did not have access to the necessary materials to get the registration under way on time.

Some would-be voters were reported to have given up waiting for the chance to register.

In Abuja, centres were open but news agencies said attendance was low.

Before the vote, Mr Obasanjo, a former military ruler who won an election set up by the country's then-military regime in 1999, has to fight against calls for his impeachment.

Legal challenge

He is accused of the misappropriation of public funds, and even members of his own party have spoken out strongly against him.

More delays to voter registration were threatened by a legal challenge from five political parties who said they were denied the 30 days notice required to mobilise supporters.

A ruling that the five parties were ineligible for the ballot was overturned last month, but the electoral commission had appealed, and the case is due before the Supreme Court.

On Wednesday, Nigeria's Federal High Court refused a request by the parties to delay the registration, clearing the way for the operation to go ahead.